On the way to work this morning I passed two policemen (looked like beat police rather than traffic police) and one had a camera on a tripod. A little bit later down the road there were 3 more policemen with no cameras. Now this is a 20mph speed limit and there are no speed camera warning signs so I wondered whether this was a speed camera or something else (maybe to detect vehicles with out of date tax etc??).
Anyone know what this was at all? Also, do there still have to be warning signs present nowadays or is this an urban myth?